OUK FRIENDS AND FOES 



137 



is hot and dry, conditions naturally favorable to the 

 increase of bugs, the farmer must rely upon artificial 

 barriers. Ridges covered with tar or similar adhesive 

 substances placed through the field prevent, the insects' 

 advance into new territory, since during their most 

 destructive period they are wingless and must proceed 

 by traveling along the ground. Post-holes placed at in- 

 tervals along the side of this ridge will trap great num- 

 bers of these invading insects. (Fig. 109.) Clean, 

 careful farming, gathering rubbish and burning the 

 same in the fall will remove opportunities for the adult 

 insects to hibernate in security. When this is done 

 many will not live to reproduce their kind the follow- 

 ing season. 



Grasshoppers.- -These frequently cause great destruc- 

 tion to cultivated crops. The most noted among the 

 destructive forms in this country is the Rocky Mountain 

 locust. This insect eludes all effective means of de- 

 fense, since it is migratory, and appears in hordes with- 

 out previous warning. 



There are, however, many native forms which live 

 and die near the place of birth. These the agriculturist 

 can readily dispose of. The life history of one of these 

 has already been studied. It has been observed that 

 they spend the winter in the egg stage in pods, about 

 one hundred in number, about an inch below the surface 

 of the soil. It is evident that if these eggs are destroyed, 

 no grasshoppers will appear to injure vegetation. This 

 should then be the first point of attack. In the fall the 

 female lays about 100 eggs, in a hole made by herself 

 and extending an inch or so beneath the surface of the 



